Nanomaterials don't move predictably in water

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ANAHEIM, Calif. — The tiniest particles of matter don’t flow uniformly in water, a finding that could have wide-ranging implications in assessing environmental risks and benefits of nanotechnology — the science of manipulating the very small, a scientist said Thursday.

Preliminary research, the first of its kind, suggests that the ways in which so-called nanoparticles behave in groundwater environments or water treatment plants are as varied as the diverse molecules or atoms used to assemble them.

The finding precludes making broad statements about how nanomaterials, measurable in the billionths of a meter, move in watery environments, said Mark Wiesner of Rice University. Details were presented at the annual meeting of the American Chemical Society.

“What’s becoming obvious is while it’s trendy to talk about nanomaterials in broad-brush terms, we can’t do that. We need to discuss this on a case-by-case basis,” Wiesner said in an interview.

Gumming up the works
The discovery also suggests limited roles for some nanoparticles in either dirtying or cleaning the world — they have been characterized as capable of doing both — since they gum up before flowing very far.

Among the minute materials examined by Wiesner and his colleagues were buckyballs, a soccer ball-shaped particle thousands of times smaller than a human hair.

Early research, presented by other scientists at the meeting, suggested the particles cause brain damage in fish.

“There are many potential benefits of nanotechnology, but its hazards and risks are poorly understood. This study gives us additional cause for concern,” said Eva Oberdorster of Southern Methodist University.

Wiesner said laboratory tests showed the particles were the least mobile from among a variety of nanomaterials his group examined, presumably reducing their potential for causing harm in the environment.

Even the nanoparticles best suited for travel appeared capable of moving underground no more than about 10 yards before sticking to larger grains of sand, he added.

Problems in fighting pollution?
The finding also could impede those who want to press the ultra-small particles into the fight against pollution.

Scientists are working to develop special nanoparticles to seek out and destroy sources of groundwater pollution that often are expensive and difficult to treat.

Wiesner said not all nanoparticles are the same — some may be incapable of “finding their targets” if injected into the ground.

The findings underscore a basic tenet of nanotechnology: “When you get smaller, properties change,” Mark Ratner of Northwestern University said during a nanotechnology forum.

The U.S. government is spending roughly $1 billion a year on nanotechnology, including dozens of studies that examine its environmental and societal impacts. The private sector is laying out billions more.

“We can’t afford to make mistakes,” American Chemical Society president Charles Casey said.